Based upon the South American favorite ceviche; in other words, raw fish “cooked” by being soaked in lemon or lime juice until slightly stiffened and opaque. I find such preparations immensely addictive in warm weather as they are, all at once, refreshing, piquant, vibrant of flavor, and as colorful as an entire trellis of sweet peas. Eat with buttered rye bread or a bowl of tiny, scrupulously scraped, hot new potatoes.